Charlie Starkweather and Caril Ann Fugate were small-town teenage lovers who went on a gruesome killing spree in 1958. Theirs is a compelling story that's inspired several outstanding cinematic adaptations. When “Love Kills,” a musical adaptation playing at the Firehouse Theatre, sticks to the development and ultimate end of Charlie and Caril Ann's relationship, it's also excellent: riveting, disturbing, darkly funny and even creepily tender.

Unfortunately, engrossing scenes played with a pitch-perfect level of adolescent angst by Nicholas Aliff (as Charlie) and Emma Orelove (as Caril Ann) are regularly interrupted by uninteresting songs and a clumsy, overwrought subplot featuring Merle, the sheriff who arrests the young killers (Larry Gard), and his wife, Gertrude (Kimberly Jones-Clark). While movies such as Oliver Stone's film “Natural Born Killers” turned Charlie and Caril Ann's story into an unsettling exploration of bloodlust and fame, “Love Kills” reduces it to a vehicle for the dreary reconciliation of a middle-aged couple.Playwright Kyle Jarrow's uneven script and score aren't bolstered in this staging overseen by director Morrie Piersol. Big problems include cast members who often fail in their best attempts to find the songs' elusive melodies. The clever lighting design (by David McLain), featuring prison walls delineated by bright white lines on the stage, is undermined when the cell “doors” don't always open, a small but distracting problem.

Issues like these almost, but don't quite, eclipse a truly brilliant performance by Aliff, a dynamic young actor with a commanding physical presence and a clear, strong voice that effortlessly soars into upper registers when required. He makes Charlie a believably menacing killer while exposing the endearingly awkward teenage boy underneath. His initial meeting with Caril Ann in a movie theater strikes all the right notes of longing and attraction, with an undercurrent of violence. He's nearly matched by Orelove who portrays Caril Ann as a lovesick girl with a bitter, wounded edge. The show's best musical moments are duets between these two, particularly the plaintive “Love Will Never Die.”

Jones-Clark tries gamely to make Gertrude a relevant part of the story, reluctantly assuming the role of mother to Caril Ann after she and Charlie are jailed. But she's saddled with the most ham-fisted of the show's songs, “Don't Falter,” and her scenes with Gard, whose exaggerated acting style seems to belong in a different show, are unaffecting.

“Love Kills” name checks “Romeo and Juliet” and “Rebel Without a Cause” along the way but, with a plot centered on extracting confessions from Charlie and Caril Ann, it doesn't come close to the dynamism of those older stories. If it weren't for exceptional performances by Aliff and Orelove, “Love Kills” would be dead on arrival. S

“Love Kills” is playing at the Firehouse Theatre Project, 1609 W. Broad St., through Nov. 20. Call 355-2001 or go to firehousetheatre.org for tickets and information.